Heat-resistant polyether, curable polyether, and coating liquid for forming a polyether film

ABSTRACT

A heat-resistant polyether having a heat resistance to a temperature of 300° C. or higher, sufficient solubility in organic solvents, low water absorption and high adhesion to substrates is provided by a heat-resistant polyether including a repeating unit represented by the formula (1) and having a polystyrene-converted weight-average molecular weight determined by GPC of not less than 1000 and not more than 50000:  
                 
 
     wherein Ar represents a bivalent organic group having an aromatic ring; R 1  to R 8  each independently represent a hydrogen atom or an aryl group which may be substituted; and when at least one of R 1  to R 8  is an aryl group which may be substituted,  
     X represents a direct bond or a hydrocarbon group having 1 to 20 carbon atoms, while when all of R 1  to R 8  are hydrogen atoms,  
     X is represented by the formula (2):  
     —CR 9 (R 10 )—  (2)  
     wherein R 9  and R 10  each independently represent an aryl group which may be substituted.

FIELD OF THE INVENTION

[0001] The present invention relates to a heat-resistant polyether, acurable polyether, a polyether film comprising the heat-resistantpolyether or the curable polyether, a coating liquid containing theheat-resistant polyether or the curable polyether for forming apolyether film, an insulating film obtained from the coating liquid, andan electronic device having the insulating film.

BACKGROUND OF THE INVENTION

[0002] Insulating films and protective films for use in electronicdevices such as ICs, LSIs and liquid crystal devices are required tohave a heat resistance to a temperature of 300° C. or higher becausetemperature sometimes rise up higher during the process formanufacturing device. While ceramic-type films such as Spin On Glass(SOG) films have been conventionally used for such insulating films andprotective films, use of organic polymers has been developed in recentyears from the viewpoints of further improvements in insulating propertyand lowering of dielectric.

[0003] Polybenzimidazole and polypyromellitimide, for example, areexcellent in heat resistance but are soluble only in strong acids suchas concentrated sulfuric acid and hence cannot be used as protectivefilms for plastics and metals.

[0004] Polyimides have high water absorption property and hence have aproblem that the strength of adhesion to substrates week.

[0005] Accordingly, it is an object of the present invention to providea heat-resistant polyether having a heat resistance to a temperature of300° C. or higher, sufficient solubility in solvent, low waterabsorption and high adhesion to substrates such as silicone wafer.

SUMMARY OF THE INVENTION

[0006] The inventors of the present invention have found that apolyether having a repeating unit represented by the formula (1) and aweight-average molecular weight converted into molecular weight ofpolystyrene determined by GPC of from 1000 to 50000 has a heatresistance to a temperature of 300° C. or higher, sufficient solubilityin solvents, low water absorption and high adhesion to substrates, andhave completed the present invention.

[0007] That is, the present invention provides a heat-resistantpolyether comprising a repeating unit represented by the formula (1) andhaving a weight-average molecular weight converted into molecular weightof polystyrene determined by GPC of from 1000 to 50000:

[0008] wherein Ar represents a bivalent organic group having an aromaticring; R¹ to R⁸ each independently represent a hydrogen atom or an arylgroup which may be substituted; and when at least one of R¹ to R⁸ is anaryl group which may be substituted,

[0009] X represents a direct bond or a hydrocarbon group having 1 to 20carbon atoms, while when all of R¹ to R⁸ are hydrogen atoms,

[0010] X is represented by the formula (2):

—CR⁹(R¹⁰)—  (2)

[0011] wherein R⁹ and R¹⁰ each independently represent an aryl groupwhich may be substituted.

[0012] The present invention also provides a curable polyethercomprising a heat-resistant polyether as described above which hasfurther a functional group capable of crosslinking reaction.

[0013] Further, the present invention provides a polyether filmcomprising a heat-resistant polyether as described above or a curablepolyether as described above, a coating liquid comprising one of thesepolyethers and an organic solvent for forming a polyether film, and aninsulating film obtained from the coating liquid, as well as anelectronic device having such an insulating film.

DETAILED DESCRIPTION OF THE INVENTION

[0014] A polyether according to the present invention is aheat-resistant polyether comprising a repeating unit represented by theformula (1) as shown above and having a weight-average molecular weightconverted into molecular weight of polystyrene determined by GPC(hereinafter, sometimes referred as the polystyrene-convertedweight-average molecular weight) of from 1000 to 50000.

[0015] If the polystyrene-converted weight-average molecular weight isless than 1000, the heat resistance of the polyether is not sufficient,while if it is more than 50000, a polyether film-forming coating liquidcomprising the polyether has an increased viscosity and hencedeteriorates coating property.

[0016] Ar in the formula (1) represents a bivalent organic group havingone or plural aromatic rings. If the organic group has plural aromaticrings, these aromatic rings may be bonded to each other either directlyor through a hydrocarbon group having 1 to 10 carbon atoms, ether group,carbonyl group, carboxyoxy group (—COO— or —OCO—), or sulfonyl group(—SO₂—).

[0017] Examples of such aromatic rings include benzene ring andnaphthalene ring. An alkyl group may be bonded to each of these rings.

[0018] Preferably, Ar is selected from the following group (A)consisting of bivalent organic groups. These are easy to produceindustrially because their dihalides derivatives are commerciallyavailable.

[0019] When at least one of R¹ to R⁸ is an aryl group which may besubstituted, X in the formula (1) is a direct bond or a hydrocarbongroup having 1 to 20 carbon atoms. The expression “X is a direct bond”,as used herein, means that benzene rings are bonded to each otherdirectly in the formula (1). There is no particular limitation on thebonding position. Since preferable X has a structure free from anyhetero-atom from the viewpoints of insulating property and low waterabsorption, the hydrocarbon group having 1 to 20 carbon atoms ispreferable and the hydrocarbon group selected from the following group(B) consisting of bivalent organic groups is more preferable:

[0020] wherein R¹¹ and R¹² each represent an aryl group which may besubstituted. Examples of such aryl groups which may be substituted foruse as R¹¹ and R¹² include those aryl groups same as exemplified for R¹and R⁸ as shown below.

[0021] When all of R¹ to R⁸ in the formula (1) are hydrogen atoms, X isrepresented by the formula (2):

—CR⁹(R¹⁰)—  (2)

[0022] wherein R⁹ and R¹⁰ each independently represent an aryl groupwhich may be substituted.

[0023] R¹ to R⁸ in the formula (1) each independently represent ahydrogen atom or an aryl group which may be substituted.

[0024] Examples of such aryl groups which may be substituted include agroup having an aromatic ring such as benzene ring or naphthalene ring.An alkyl group may be bonded to such an aromatic ring. Such an arylgroup may have one or plural aromatic rings. When the aryl group hasplural aromatic rings, the rings may be bonded to each other eitherdirectly or through an alkylene group having 1 to 3 carbon atoms,alkenylene group having 2 or 3 carbon atoms, alkynylene group having 2or 3 carbon atoms, ether group, carbonyl group, carboxyoxy group, orsulfonyl group.

[0025] Specific examples of R¹ to R⁸ include phenyl group, naphthylgroup, biphenyl group, terphenyl group, toluyl group, ethylphenyl group,propylphenyl group, dimethylphenyl group, diphenylphenyl group,dimethylnaphthyl group, ethylnaphthyl group, propylnaphthyl group,methylbiphenyl group, dimethylbiphenyl group, trimethylbiphenyl group,methylterphenyl group, dimethylterphenyl group, trimethylterphenylgroup, tetramethylterphenyl group, phenyloxyphenyl group,toluyloxyphenyl group, dimethylphenyloxyphenyl group,trimethylphenyloxyphenyl group, diphenoxyphenyl group, phenylketophenylgroup, methylphenylketophenyl group, dimethylphenylketophenyl group,benzylphenyl group, phenylethylphenyl group, phenylpropylphenyl group,phenylbutylphenyl group, phenylhexylphenyl group, phenylethynylphenylgroup, phenylpropylphenyl group, phenylbutenylphenyl group,phenylethenylphenyl group, phenylpropynylphenyl group, andphenylsulfonylphenyl group.

[0026] R⁹ and R¹⁰ in the formula (2) each represent an aryl group whichmay be substituted. Examples of such aryl groups include those arylgroups same as exemplified for R¹ to R⁸.

[0027] More preferable aryl groups which may be substituted for use asR¹ to R¹⁰ are those having one to three aromatic rings. In the case ofan aryl group having two or more aromatic rings, it is preferred that acarbon atom directly bonded to such aromatic rings as a combining grouphas no hydrogen atom. If a carbon atom directly bonded to aroma-ticrings has any hydrogen atom, the resulting polyether may be deterioratedby autoxidation, so that decomposition of the polyether is likely to befacilitated under a heat treatment in the presence of oxygen.

[0028] Among such aryl groups which may be substituted, particularlypreferable are those aryl groups having two or less aromatic rings ofthe following group (C):

[0029] wherein R¹³ to R¹⁶ each independently represent an alkyl grouphaving 1 to 3 carbon atoms.

[0030] If the aryl group has three or more aromatic rings, thereactivity of group Y, which is a reactive site of a monomer representedby the following formula (4) or (5) for the preparation of thepolyether, is lowered due to steric hindrance, with the result that thetime period required for polymerization tends to become longer.

[0031] wherein R¹ to R⁸ and X each are the same as in the formula (1);R⁹ to R¹⁰ each are the same as in the formula (2); and Y represents ahydroxyl group, trimethylsilyloxy group, fluorine atom, chlorine atom,bromine atom, iodine atom, mesyl group, or tosyl group.

[0032] In view of making polymerization time period shorter, it isparticularly preferred that at least one of R¹ to R⁸ in the formula (1)or at least one of R⁹ and R¹⁰ in the formula (2) be a phenyl group.Monomers each having a phenyl group are those of the following group (E)for example. These monomers are preferable because they are commerciallyavailable.

[0033] The heat-resistant polyether of the present invention, forexample, may be obtained through condensation polymerization of themonomer represented by the formula (4) or (5) above. The monomerrepresented by the formula (4) or (5) may be a commercially-availableproduct, for example, a bisphenol monomer having a hydroxyl group as Yor may be synthesized from a corresponding phenol and a ketone, aldehydeor the like having the group X with use of a strong acid such assulfuric acid or trifluoroacetic acid as a catalyst. If the bisphenolmonomer is reacted with tosyl chloride or mesyl chloride, for example, amonomer having a tosyl or mesyl group as Y can be synthesized. On theother hand, a monomer having a halogen as Y can be synthesized bydirectly halogenating a corresponding aromatic compound withbromine/bromine chloride or iodine/silver sulfate for example.

[0034] The intended polymer can be prepared by condensation-polymerizinga hydroxyl group represented by the formula (4) or (5), which is thussynthesized by the method described above, with a halogen, tosyl groupor mesyl group via inter- or intra-molecular condensation. Thecondensation polymerization may be conducted under usual conditions. Forexample, the condensation polymerization is conducted under theconditions:

[0035] Catalyst: alkaline catalyst,

[0036] co-catalyst: copper salt such as copper chloride or copperbromide, or copper-pyridine complex,

[0037] condensation-polymerization temperature: 80-200° C.,

[0038] condensation-polymerization time period: 0.5-30 hours.

[0039] Next, description will be made of the curable polyether of thepresent invention. The curable polyether comprises a heat-resistantpolyether having the repeating unit represented by the formula (1)further having a functional group in a molecular chain thereof, thefunctional group being capable of crosslinking reaction. The“crosslinking reaction”, as used herein, means a reaction causing newlinkage to occur between two or more functional groups of the polymer.The crosslinking reaction is caused by heating or UV irradiation.Examples of such crosslinking reactions include radical additionreaction causing carbon-carbon unsaturated groups to be coupled to eachother, Diels-Alder reaction between a conjugated diene and acarbon-carbon unsaturated group, 1,3-dipolar addition reaction betweenan azido group, a nitrile oxide group and a carbon-carbon unsaturatedgroup, and reaction to produce siloxane through dehydrocondensationbetween silanol groups.

[0040] The number of such functional groups per one repeating unitrepresented by the formula (1) is about 0.01 to about 2, preferably 0.05to 1.5.

[0041] In general, the functional group capable of crosslinking reactionmay be introduced into the heat-resistant polyether that has beenprepared in advance.

[0042] The functional group is preferably a functional group having acarbon atom directly bonded to an aromatic ring and no hydrogen atomfrom the viewpoint of heat resistance of the obtained polymer.Specifically, such preferable functional groups include those functionalgroups selected form the following group (D) or represented by theformula (3).

[0043] wherein T¹ and T² each represent a hydrogen atom, an alkyl grouphaving 1 to 3 carbon atoms, or an aryl group which may be substituted;and T³ and T⁴ each represent an alkyl group having 1 to 3 carbon atomsor an aryl group which may be substituted.

[0044] wherein T⁵ represents an alkenyl group having 2 or 3 carbon atomsor an alkynyl group having 2 or 3 carbon atoms; T⁶ represents an alkylgroup having 1 to 3 carbon atoms or an aryl group which may besubstituted; n is 1, 2 or 3; when n is 2 or 3, T⁵'s may be the same ordifferent, while when n is 1, T⁶'s may be the same or different; and T¹to T⁶ are the same or different with each other.

[0045] Examples of functional groups selected from the group (D) includevinyl group, allyl group, propenyl group, isopropenyl group, butenylgroup, hexenyl group, 2-methyl-2-propenyl group, 2,2-diphenylvinylgroup, styryl group, naphthalenevinylene group, toluylenevinylene group,ethynyl group, propargyl group, propynyl group, butynyl group, hexynylgroup, phenylacetylene group, and naphthylacetylene group.

[0046] Examples of functional groups represented by the formula (3)include vinyldimethylsilyl group, vinyldiethylsilyl group,vinyldipropylsilyl group, vinyldiphenylsilyl group, vinyldinaphthylsilylgroup, vinylmethylnaphthylsilyl group, vinyldimethylsilyl group,vinyldiethylsilyl group, vinyldipropylsilyl group, vinyldiphenylsilylgroup, divinylmethylsilyl group, divinylethylsilyl group,divinylpropylsilyl group, divinylphenylsilyl group, allyldimethylsilylgroup, allyldiethylsilyl group, allyldipropylsilyl group,allyldiphenylsilyl group, allyldinaphthylsilyl group,allylmethylnaphthylsilyl group, allyldimethylsilyl group,allyldiethylsilyl group, allyldipropylsilyl group, allyldiphenylsilylgroup, diallylmethylsilyl group, diallylethylsilyl group,diallylpropylsilyl group, diallylphenylsilyl group, butenyldimethylsilylgroup, butenyldiethylsilyl group, pentenyldimethylsilyl group,pentenyldiethylsilyl group, octenyldimethylsilyl group,decanyldimethylsilyl group, trivinylsilyl group, triallylsilyl group,tributenylsilyl group, trioctenylsilyl group, vinyldiallylsilyl group,divinylallysilyl group, and divinyloctenylsilyl group.

[0047] The functional group represented by the formula (3) is preferableas the functional group capable of crosslinking reaction by heating,since it may be easily introduced into the heat-resistant polyether ofthe present invention on the grounds that: it is easy to obtainhalogenated silane as a precursor of the functional group; and thereactivity of its silicon-halogen bond is high enough.

[0048] Among them, trivinylsilyl group is suitably used because acurable polyether obtained by introduction of this group has so highcrosslinking reactivity that crosslinking is achieved at a lowtemperature.

[0049] In the case of forming a film by drying a coating liquid as willbe described later, if the coating liquid comprises the curablepolyether, the curable polyether may have a crosslinked structurethrough heating or UV irradiation performed in the film-forming process.The curable polyether having a crosslinked structure is a curablepolyether having a three-dimensional network structure resulting fromsuch crosslinking reaction. Either a part or all of the functionalgroups capable of crosslinking reaction may be crosslinked.

[0050] The coating liquid for forming a polyether film according to thepresent invention comprises the aforementioned heat-resistant polyetheror the aforementioned curable polyether, and an organic solvent.

[0051] Examples of organic solvents for use in the coating liquidinclude alcohols such as methanol, ethanol, isopropyl alcohol, butanol,t-butyl alcohol, methoxymethanol, 2-methoxyethanol, 2-ethoxyethanol,4-ethoxybutanol, cyclohexyl alcohol, and furfuryl alcohol; esters suchas ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate,propylene glycol monomethyl ether acetate, methyl propionate, ethylpropionate, methyl butyrate, ethyl butyrate, ethyl lactate, and propyllactate; ketones such as 2-pentanone, 3-pentanone, 2-hexanone,3-hexanone, methyl isobutyl ketone, 2-heptanone, 3-heptanone,acetylacetone, cyclopentanone, and cyclohexanone; ethers such as diethylether, dibutyl ether, tetrahydrofuran, tetrahydropyran, andmethyltetrahyropyran; phenol ethers such as anisole, phenetole,veratrole, diphenyl ether; carbonates such as dimethyl carbonate anddiethyl carbonate; and aromatic hydrocarbons such as toluene, xylene,and mesitylene. These may be used either alone or as mixtures of atleast two of them.

[0052] The concentration of polyether in the polyether film-formingcoating liquid is preferably from 5% to 40% by weight, more preferablyfrom 10% to 20% by weight. If the concentration of polyether is lessthan 5% by weight, the spin coating process, if employed for coating,may require application of the coating liquid several times to attain adesired film thickness because thickness formed by this process is thin.On the other hand, if the polyether concentration is more than 40% byweight, the feeding of the coating liquid or the like during coating maybecome troublesome due to an increase in the viscosity of the coatingliquid.

[0053] The polyether film-forming coating liquid of the presentinvention may include additives such as a surface-active agent and anantioxidant unless they deteriorate the chemical resistance of thecoating liquid and the strength of a film formed from the coatingliquid. In the case where the functional group capable of crosslinkingreaction has an unsaturated group, a catalyst, such as a peroxide or anazo compound, mat be added to the coating liquid because thecrosslinking reaction may occur at lower temperature by adding thesecatalyst.

[0054] The polyether film-forming coating liquid of the presentinvention is capable of forming a heat-resistant polyether film or acurable polyether film through a process including: for example,applying the coating liquid onto an electronic device by spin coating ordipping; removing the solvent; and allowing the coating liquid thusapplied to cure through a heat treatment, irradiation of light or othermethod if necessary.

[0055] The polyether film-forming coating liquid of the presentinvention is capable of coating substrates of metal, ceramic, plastic orglass thereby imparting them with a heat resistance.

[0056] A heat-resistant or curable polyether film formed from thepolyether film-forming coating liquid can be used as an insulating filmor protective film for use in an electronic device. The polyether filmof the present invention can be particularly suitably used as aninsulating film for maintaining insulation between adjacentinterconnecting metal wires of aluminum, copper or an alloy thereof.Alternatively, since the polyether film has low water absorption, it maybe used also as a protective film for protecting an electronic device inwhich a circuit has already been formed against intrusion of water ormetal ion from the external environment.

[0057] When the polyether film is to be used as an insulating film, thefilm may be rendered the dielectric constant lower by making the filmporous by any method. Since lowering the dielectric constant of thepolyether film by making the film porous is due to a change in thephysical form but not in the chemical structure of the polyether film,chemical characteristics, such as a high heat resistance, of the filmare maintained.

EXAMPLE

[0058] Hereinafter, the present invention will be described morespecifically by way of examples, which should not be construed to limitthe scope of the present invention.

Example 1

[0059] A four neck flask of 500 ml was charged with 34 g (0.08 mol) of1,1-bis(4-hydroxy-3-phenylphenyl)cyclohexylidene, 6.4 g of caustic soda,110 g of benzophenone and 60 g of toluene to allow reflux dehydration toproceed. After completion of dehydration, 25 g (0.08 mol) ofdibromobiphenyl was added into the flask. Further, a mixed liquid ofcuprous chloride-pyridine was added into the flask as a catalyst, andthe mixture in the flask was allowed to react at an internal temperatureof from 170 to 190° C. for 8 hours. After having been cooled to roomtemperature, the reaction liquid was diluted with tetrahydrofuran, andthe diluted liquid was added to a large quantity of a mixed liquid ofmethanol-acetic acid to precipitate a reaction product. The precipitatedcrystal was filtered, washed with a large quantity of methanol and thendried under reduced pressure, to give a polyether. Thepolystyrene-converted weight-average molecular weight of this polyetherdetermined by GPC (with HLC8120 manufactured by TOSOH CO., column:TSKgel SuperH 3000, developer: tetrahydrofuran at a flow rate of 0.8ml/min) was 4600. This polyether is referred to as resin A. The thermaldecomposition temperature of resin A determined by thermogravimetricanalysis (with DTA-60 manufactured by SHIMADZU CO., representation with0.1 wt % reduction under a heat-up condition of 10° C./min) was 390° C.

Example 2

[0060] A four neck flask of 500 ml was charged with 30 g (0.080 mol) of1,1-bis(4-hydroxy-3-phenylphenyl)isopropylidene, 6.4 g of caustic soda,110 g of benzophenone and 60 g of toluene to allow reflux dehydration toproceed. After completion of dehydration, 25 g (0.08 mol) ofdibromobiphenyl was added into the flask. Further, a mixed liquid ofcuprous chloride-pyridine was added into the flask as a catalyst, andthe mixture in the flask was allowed to react at an internal temperatureof from 170 to 190° C. for 6 hours. After having been cooled to roomtemperature, the reaction liquid was diluted with tetrahydrofuran, andthe diluted liquid was added to a large quantity of a mixed liquid ofmethanol-acetic acid to precipitate a reaction product. The precipitatedcrystal was filtered, washed with a large quantity of methanol and thendried under reduced pressure, to give a polyether. Thepolystyrene-converted weight-average molecular weight of this polyetherwas 4600. The polyether thus obtained is referred to as resin B. Thethermal decomposition temperature of resin B determined bythermogravimetric analysis was 380° C.

Example 3

[0061] A four neck flask of 500 ml was charged with 28 g (0.080 mol) ofbis(4-hydroxyphenyl)diphenylmethane, 6.4 g of caustic soda, 110 g ofbenzophenone and 60 g of toluene to allow reflux dehydration to proceed.After completion of dehydration, 25 g (0.080 mol) of dibromobiphenyl wasadded into the flask. Further, a mixed liquid of cuprouschloride-pyridine was added into the flask as a catalyst, and themixture in the flask was allowed to react at an internal temperature offrom 170 to 190° C. for 20 hours. After having been cooled to roomtemperature, the reaction liquid was diluted with tetrahydrofuran, andthe diluted liquid was added to a large quantity of a mixed liquid ofmethanol-acetic acid to precipitate a reaction product. The precipitatedcrystal was filtered, washed with a large quantity of methanol and thendried under reduced pressure, to give a polyether. Thepolystyrene-converted weight-average molecular weight of this polyetherwas 3700. The polyether thus obtained is referred to as resin C. Thethermal decomposition temperature of resin C determined bythermogravimetric analysis was 430° C.

Example 4

[0062] A four neck flask of 500 ml was charged with 28 g (0.056 mol) of9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 6.6 g of caustic soda, 110 gof benzophenone and 60 g of toluene to allow reflux dehydration toproceed. After completion of dehydration, 17 g (0.056 mol) ofdibromobiphenyl was added into the flask. Further, a mixed liquid ofcuprous chloride-pyridine was added into the flask as a catalyst, andthe mixture in the flask was allowed to proceed at an internaltemperature of from 170 to 190° C. for 14 hours. After having beencooled to room temperature, the reaction liquid was diluted withtetrahydrofuran, and the diluted liquid was added to a large quantity ofa mixed liquid of methanol-acetic acid to precipitate a reactionproduct. The precipitated crystal was filtered, washed with a largequantity of methanol and then dried under reduced pressure, to give apolyether. The polystyrene-converted weight-average molecular weight ofthis polyether was 1500. The polyether thus obtained is referred to asresin D. The thermal decomposition temperature of resin D determined bythermogravimetric analysis was 400° C.

Example 5

[0063] Into a four neck flask of 300 ml, the internal atmosphere ofwhich had bee replaced with nitrogen, were put 10 g of the polyetherresin obtained in EXAMPLE 1 as a raw material and 200 ml oftetrahydrofuran as a solvent, to cause the polyether resin to bedissolved in the solvent. After the internal temperature of the flaskhad been lowered to 5° C. or lower by cooling, the solution was admixedwith 17 ml of n-butyllithium (in 1.6 Mn-hexane solution) and thenstirred for one hour in a stream of nitrogen. Thereafter, 4.1 g oftrivinylsilyl chloride was added dropwise to the resulting mixture inone hour, followed by continuous stirring at the same temperature forabout one hour. Further, the internal temperature of the flask wasraised to room temperature, and then the mixture was continuouslystirred for one hour. After completion of the reaction, the reactionsolution was charged into a large quantity of a mixed liquid ofmethanol-acetic acid to cause a high-molecular weight substance toprecipitate, and the precipitated high-molecular weight substance wasfiltered and then washed with methanol and with water, to give a curablepolyether. The polystyrene-converted weight-average molecular weight ofthis curable polyether determined by GPC was 5500. According toverification of the introduction of trivinylsilyl group by ¹H-NMR, thenumber of trivinylsilyl groups introduced per one repeating unit was0.7. The polyether thus obtained is referred to as resin E. The thermaldecomposition temperature of resin E determined by thermogravimetricanalysis was 480° C.

Example 6

[0064] Into a four neck flask of 300 ml, the internal atmosphere ofwhich had bee replaced with nitrogen, were put 9.3 g of the polyetherresin obtained in EXAMPLE 2 as a raw material and 190 ml oftetrahydrofuran as a solvent, to cause the polyether resin to bedissolved in the solvent. After the internal temperature of the flaskhad been lowered to 5° C. or lower by cooling, the solution was admixedwith 17 ml of n-butyllithium (in 1.6 Mn-hexane solution) and thenstirred for one hour in a stream of nitrogen. Thereafter, 4.1 g oftrivinylsilyl chloride was added dropwise to the resulting mixture inone hour, followed by continuous stirring at the same temperature forabout one hour. Further, the internal temperature of the flask wasraised to room temperature, and then the mixture was continuouslystirred for one hour. After completion of the reaction, the reactionsolution was charged into a large quantity of a mixed liquid ofmethanol-acetic acid to cause a high-molecular weight substance toprecipitate, and the precipitated high-molecular weight substance wasfiltered and then washed with methanol and with water, to give 8.7 g ofa curable polyether. The polystyrene-converted weight-average molecularweight of this curable polyether determined by GPC was 9500. Accordingto verification of the introduction of trivinylsilyl group by ¹H-NMR,the number of trivinylsilyl groups introduced per one repeating unit was1.2. The polyether thus obtained is referred to as resin F. The thermaldecomposition temperature of resin F determined by thermogravimetricanalysis was 480° C.

Example 7

[0065] Into a four neck flask of 300 ml, the internal atmosphere ofwhich had been replaced with nitrogen, were put 3.0 g of the polyetherresin obtained in EXAMPLE 3 as a raw material and 60 ml oftetrahydrofuran as a solvent, to cause the polyether resin to bedissolved in the solvent. After the internal temperature of the flaskhad been lowered to 5° C. or lower by cooling, the solution was admixedwith 7.4 ml of n-butyllithium (in 1.6 Mn-hexane solution) and thenstirred for one hour in a stream of nitrogen. Thereafter, 1.1 g ofdimethylvinylsilyl chloride was added dropwise to the resulting mixturein one hour, followed by continuous stirring at the same temperature forabout one hour. Further, the internal temperature of the flask wasraised to room temperature, and then the mixture was continuouslystirred for one hour. After completion of the reaction, the reactionsolution was charged into a large quantity of a mixed liquid ofmethanol-acetic acid to cause a high-molecular weight substance toprecipitate, and the precipitated high-molecular weight substance wasfiltered and then washed with methanol and with water, to give a curablepolyether. The polystyrene-converted weight-average molecular weight ofthis curable polyether determined by GPC was 2500. According toverification of the introduction of dimethylvinylsilyl group by ¹H-NMR,the number of dimethylvinylsilyl groups introduced per one repeatingunit was 0.1. The polyether thus obtained is referred to as resin G. Thethermal decomposition temperature of resin G determined bythermogravimetric analysis was 440° C.

Example 8

[0066] Into a four neck flask of 300 ml, the internal atmosphere ofwhich had bee replaced with nitrogen, were put 14 g of the polyetherresin obtained in EXAMPLE 4 as a raw material and 130 ml oftetrahydrofuran as a solvent, to cause the polyether resin to bedissolved in the solvent. After the internal temperature of the flaskhad been lowered to 5° C. or lower by cooling, the solution was admixedwith 27 ml of n-butyllithium (in 1.6 Mn-hexane solution) and thenstirred for one hour in a stream of nitrogen. Thereafter, 4.0 g ofdimethylvinylsilyl chloride was added dropwise to the resulting mixturein one hour, followed by continuous stirring at the same temperature forabout one hour. Further, the internal temperature of the flask wasraised to room temperature, and then the mixture was continuouslystirred for one hour. After completion of the reaction, the reactionsolution was charged into a large quantity of a mixed liquid ofmethanol-acetic acid to cause a high-molecular weight substance toprecipitate, and the precipitated high-molecular weight substance wasfiltered and then washed with methanol and with water, to give a curablepolyether. The polystyrene-converted weight-average molecular weight ofthis curable polyether determined by GPC was 1600. According toverification of the introduction of dimethylvinylsilyl group by ¹H-NMR,the number of dimethylvinylsilyl groups introduced per one repeatingunit was 0.6. The polyether thus obtained is referred to as resin H. Thethermal decomposition temperature of resin H determined bythermogravimetric analysis was 400° C.

Examples 9-11

[0067] Resins E F and H were each dissolved in anisole so that theresulting solution had a solid content of 15%, and the solution wasfiltered with a 0.1-μm PTFE filter. A 4-inch silicon wafer was coatedwith the solution thus obtained by spin coating at 2000 rpm, baked at150° C. for one minute, and then heat-treated at 400° C. for 30 minutesin a nitrogen atmosphere. The thickness of the resulting film wasmeasured using an optical thicknessmeter (NANOSPEC 210 manufactured byNANOMETRIC CO.), while the relative dielectric constant of the film wasdetermined by C-V measurement (with SSM495 model manufactured by SSMCO.) at an operating frequency of 1 MHz according to the mercury probemethod. Further, the adhesion of the film was determined by theSebastian test. The results are shown in Table 1. TABLE 1 Example ResinRelative Dielectric Constant Adhesion 9 E 2.8 >70 10 F 2.8 >70 11 H 2.8>70

Examples 12-14

[0068] Resin D was dissolved in 2-heptanone so that the resultingsolution had a solid content of 15%, and the solution was filtered witha 0.1-μm PTFE filter. A 4-inch silicon wafer was coated with thesolution thus obtained by spin coating at 2000 rpm, baked at 150° C. forone minute. Thereafter the wafer was maintained at 350-400° C. for 3hours in a nitrogen atmosphere to determine thickness decreasing ratesper one hour of the film. The results are shown in TABLE 2. TABLE 2 Heattreatment Amount of decrease in Example temperature thickness 12 350° C.<0.1%/Hr 13 375° C. <0.1%/Hr 14 400° C.  1.2%/Hr

Examples 15-17

[0069] The wafers coated in EXAMPLES 9-11 were each immersed inultrapure water at room temperature and allowed to stand therein forfive hours. Each of the wafers was removed from ultrapure water,spin-dried and then baked at 150° C. for one minute. The film coatingeach wafer was measured as to its relative dielectric constant in thesame manner as in EXAMPLES 9-11. As seen from TABLE 3, any rise indielectric constant due to absorption of water in particular was notnoticed. Further, it was confirmed by FT-IR analysis that there wasfound no water absorption peak within the range between 3000 cm⁻¹ and3300 cm⁻¹. TABLE 3 Relative Occurrence of dielectric water absorptionconstant after peak found by FT- Example Wafer used treatment IRanalysis 15 Example 9  2.8 Not found 16 Example 10 2.8 Not found 17Example 11 2.8 Not found

Example 18

[0070] Resin H is dissolved in anisole so that the resulting solutionhas a solid content of 15%. Further, a foaming agent is added to thesolution so that the resulting foamed material produced after a heattreatment at 400° C. has a porosity of 20%. The solution is treated inthe same manner as in EXAMPLE 9 to for a porous polyether film over awafer. The relative dielectric constant of this polyether film can belowered to 2.6.

[0071] According to the present invention, it is possible to provide aheat-resistant polyether having a superior heat resistance, satisfactorysolubility in organic solvents, low water absorption, and high adhesionto substrates.

What is claimed is:
 1. A heat-resistant polyether comprising a repeating unit represented by the formula (1) and having a polystyrene-converted weight-average molecular weight determined by GPC of from 1000 to 50000:

wherein Ar represents a bivalent organic group having an aromatic ring; R¹ to R⁸ each independently represent a hydrogen atom or an aryl group which may be substituted; and when at least one of R¹ to R⁸ is an aryl group which may be substituted, X represents a direct bond or a hydrocarbon group having 1 to 20 carbon atoms, while when all of R¹ to R⁸ are hydrogen atoms, X is represented by the formula (2): —CR⁹(R¹⁰)—  (2)  wherein R⁹ and R¹⁰ each independently represent an aryl group which may be substituted.
 2. The heat-resistant polyether according to claim 1, wherein Ar is one selected from the following group (A) consisting of bivalent organic groups:


3. The heat-resistant polyether according to claim 1 or 2, wherein the hydrocarbon group having 1 to 20 carbon atoms as X is one selected from the following group (B) consisting of bivalent organic groups:

 wherein R¹¹ and R¹² each represent an aryl group which may be substituted.
 4. The heat-resistant polyether according to claim 1, wherein at least one of R¹ to R⁸ is one selected from the following group (C) consisting of aryl groups:

 wherein R¹³ to R¹⁶ each independently represent an alkyl group having 1 to 3 carbon atoms.
 5. The heat-resistant polyether according to claim 1, wherein at least one of R⁹ and R¹⁰ in the formula (2) is one selected from the following group (C) consisting of aryl groups:

 wherein R¹³ to R¹⁶ each independently represent an alkyl group having 1 to 3 carbon atoms.
 6. The heat-resistant polyether according to claim 1, wherein at least one of R¹ to R⁸ in the formula (1) is a phenyl group.
 7. The heat-resistant polyether according to claim 1, wherein at least one of R⁹ to R¹⁰ in the formula (2) is a phenyl group.
 8. A curable polyether comprising a heat-resistant polyether as recited in claim 1, the heat-resistant polyether further having a functional group capable of crosslinking reaction.
 9. The curable polyether according to claim 8, wherein the functional group capable of causing a crosslinking reaction to occur under heating is one selected from the following group (D) consisting of functional groups:

 wherein T¹ and T² each represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or an aryl group which may be substituted; and T³ and T⁴ each represent an alkyl group having 1 to 3 carbon atoms or an aryl group which may be substituted.
 10. The curable polyether according to claim 8, wherein the functional group capable of causing a crosslinking reaction to occur under heating is a functional group represented by the formula (3):

 wherein T⁵ represents an alkenyl group having 2 or 3 carbon atoms or an alkynyl group having 2 or 3 carbon atoms; T⁶ represents an alkyl group having 1 to 3 carbon atoms or an aryl group which may be substituted; n is 1, 2 or 3; and when n is 2 or 3, T⁵'s are the same or different, while when n is 1, T⁶'s are the same or different.
 10. The curable polyether according to claim 9, wherein T⁵ and T⁶ are each a vinyl group.
 11. The curable polyether according to claim 8, which has a crosslinked structure.
 12. A heat-resistant polyether film comprising a heat-resistant polyether as recited in claim
 1. 13. A curable polyether film comprising a curable polyether as recited in claim
 8. 14. A coating liquid for forming a polyether film, comprising a heat-resistant polyether as recited in claim 1, and an organic solvent.
 15. A coating liquid for forming a polyether film, comprising a curable polyether as recited in claim 8, and an organic solvent.
 16. An insulating film obtained from a coating liquid for forming a polyether film as recited in claim
 14. 17. An insulating film obtained from a coating liquid for forming a polyether film as recited in claim
 15. 18. An electronic device comprising an insulating film as recited in claim 16 or
 17. 